This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | -1 |
| 2 | -1 |
| 3 | -1 |
| 4 | 23 |
| 5 | -51 |
| 6 | 35 |
| 7 | -197 |
| 8 | 1367 |
| 9 | -3889 |
| 10 | 7649 |
| 11 | -26258 |
| 12 | 112739 |
| 13 | -350676 |
| 14 | 939623 |
| 15 | -3063201 |
| 16 | 11022167 |
| 17 | -35276497 |
| 18 | 106320311 |
| 19 | -344831533 |
| 20 | 1164544273 |
| 21 | -3765456206 |
| 22 | 11890410454 |
| 23 | -38631658591 |
| 24 | 127610160227 |
| 25 | -414671018176 |
| 26 | 1335126443260 |
| 27 | -4348160271568 |